Among the therapeutic procedures applicable to the present invention are percutaneous transluminal coronary angioplasty (PTCA) and stenting. These procedures can be used, for example, to reduce arterial build-up of cholesterol fats or atherosclerotic plaque. During such an intervention, a guiding catheter is used to form a direct conduit from outside a patient's body, through the vasculature to the site targeted for treatment or to the ostium of the diseased artery. Before performing an intervention, an angiography catheter may be utilized to diagnose the patient's symptoms by injecting radiopaque contrast into suspected arteries, creating fluoroscopic images.
Guiding catheters and angiography catheters must have sufficient bending stiffness to be pushed through vessels as well as sufficient torsional rigidity to provide a high degree of torsional control. It is also desirable for a catheter to have a soft or flexible distal tip to avoid dangers of puncturing or otherwise damaging a vessel as it twists through the vascular system. Examples of such soft tip catheters are known in the art. Guiding catheters and angiography catheters generally are formed as a three-layer composite tube. The first layer is a hollow liner, which, in the case of a guiding catheter, is provided with a lubricious inner surface to aid in device passage through the lumen of the catheter. The next layer is a reinforcing material, typically a stainless steel wire that is braided around the liner. An outer jacket encapsulates the braid and is bonded to the liner through braid interstices to create a monolithic structure from the three components.
The trend in the field of the invention has been toward catheters having thinner walls with a goal of providing a larger lumen, a smaller outside diameter, or both. While improvements in polymeric materials used for catheter liners and/or jackets have helped in the achievement of thinner walls, the thickness of the common braided reinforcement layer has become a limitation to further progress in this area. To create a woven braid, filaments must be passed over other filaments, giving the reinforcement layer, in effect, twice the thickness of the filaments. Additionally, despite their encapsulation between the outer jacket and the liner, braid filaments are not secured together at their intersections, so that the filaments can shift relative to each other, thus diminishing physical properties of the catheter such as torsional stiffness and kink resistance.
The prior art includes references that teach forming a catheter reinforcement layer by spirally wrapping a perforated film around a liner, or by rolling a patterned sheet to form a catheter tube. To create an uninterrupted layer of reinforcement material, such examples require a double-thickness overlapping seam or an unsecured butt seam, which has compromised physical properties. Thus, there is a continuing need for improvements in reinforced catheters having reduced wall thickness while maintaining good or improved properties of stiffness, torque transfer characteristics and high kink resistance.